THE  UNIVERSITY 

OF  ILLINOIS 

LIBRARY 

630.7 

II6b 
nos.as4.-4-5 


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A6R1CULTURAL 
UIBM 


UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station 


BULLETIN   NO.  226 


VARIATIONS  IN  FARROW:  WITH  SPECIAL 
REFERENCE  TO  THE  BIRTH  WEIGHT  OF  PIGS 

BY  W.  J.  CARMICHAEL  AND  JOHN  B.  EICE 


URBANA,  ILLINOIS,  MAY,  1920 


CONTENTS  OF  BULLETIN  No.  226 

PAGE 
OBJECT  AND  PLAN  OF  WORK 67 

LENGTH  OF  GESTATION  PERIOD 68 

SIZE  OF  LITTER 71 

AGE  OF  DAM 73 

BREED 74 

TIME  OF  YEAR 75 

ORDER  OF  FARROWING 75 

SUCCEEDING  LITTERS  FROM  THE  SAME  Sow 76 

SUMMARY  AND  CONCLUSIONS 77 

INDEX  TO  TABLES 79 

TABLES  .  .  80 


VARIATIONS  IN  FARROW:    WITH  SPECIAL 
REFERENCE  TO  THE  BIRTH  WEIGHT  OF  PIGS 

BY  W.  J.  CARMICHAEL,  ASSOCIATE  IN  ANIMAL  HUSBANDRY1,  AND 
JOHN  B.  EICE,  ASSOCIATE  IN  ANIMAL  HUSBANDKY 

OBJECT   AND   PLAN   OF   WORK 

The  object  of  this  research  has  been  to  study  the  variations  in 
farrow  among  the  several  breeds  of  swine,  together  with  some  of 
the  factors  other  than  breed  that  may  cause  noticeable  differences 
among  the  litters  at  the  time  of  birth. 

The  breeding  and  farrowing  records  which  have  been  kept  in 
connection  with  the  herd  of  swine  under  the  management  of  the  Ani- 
mal Husbandry  Department  of  the  University  of  Illinois,  during  the 
years  1903  to  1916  inclusive,  have  furnished  the  data  for  this  study. 
These  records  include  720  litters  containing  5,840  pigs  of  seven  dis- 
tinct breeds  and  a  number  of  different  crosses,  as  well  as  a  few 
litters  the  exact  breeding  of  which  is  not  definitely  known.  Com- 
plete information  was  not  obtained  in  connection  with  every  litter, 
but  an  attempt  was  made  to  secure:  (a)  the  breeding  of  sire  and 
dam;  (b)  age  of  dam;  (c)  length  of  gestation  period;  (d)  number 
of  pigs  in  the  litter;  (e)  sex  of  the  pigs;  (f)  order  of  farrowing; 
(g)  individual  weight  of  pigs;  and  (h)  the  number  of  pigs  farrowed 
dead  or  immature. 

For  the  most  part  the  records  were  kept  by  the  herdsman  actively 
in  charge  at  the  barns.  The  information  contained  on  his  records 
was  copied  into  the  permanent  records  of  the  office,  from  which  the 
data  for  this  study  were  taken.  Where  there  was  any  doubt  as  to 
the  accuracy  of  the  data,  it  was  assumed  that  there  was  no  in- 
formation on  that  particular  phase  in  connection  with  the  litter  in 
question.  However,  there  has  been  no  attempt  to  eliminate  any 
litters  produced  by  sows  on  any  specific  ration  or  under  any  par- 
ticular conditions,  nor  has  there  been  any  elimination  other  than 
that  necessitated  by  lack  of  data  or  obvious  error  in  the  information 
collected.  All  litters  farrowed  in  the  herd  within  the  given  years 
have  therefore  been  considered  in  this  study  so  far  as  the  data  would 
permit. 

Individual  pig  weights  were  taken  before  the  pigs  were  allowed 
to  suckle,  tested  spring  balance  scales  being  used  for  this  purpose* 
and  the  weights  were  recorded  by  pounds  and  tenths.  In  case  it 


*Now  Secretary  of  the  National  Swine  Growers'  Association. 

67 


68  BULLETIN  No.  226  [May, 

was  not  possible  to  get  the  birth  weights  in  the  order  of  farrowing, 
the  pigs  were  weighed  individually  as  soon  thereafter  as  possible, 
and  the  fact  that  the  order  of  farrowing  was  not  obtained  was  noted 
on  the  record.  In  some  cases  individual  weights  were  not  obtained 
because  a  few  hours'  time  had  elapsed  before  there  was  an  opportu- 
nity to  make  such  weighings.  In  those  cases  the  litter  weights,  even 
tho  taken,  were  not  used  for  this  study. 

The  rations  on  which  the  sows  were  fed  and  the  method  of  feed- 
ing and  handling  doubtless  caused  some  of  the  variations  herein- 
after noted.  However,  the  rations  have  not  been  considered  since 
the  feed  records  are  not  complete  for  the  entire  number  of  sows  nor 
for  a  sufficient  number  of  them  to  make  such  a  study  of  much  value. 
The  herd  sows  have  in  general  been  handled  similar  to  those  in  many 
herds  of  pure-bred  swine. 

A  very  systematic  study  of  the  field  is  difficult  since  so  many 
factors  may  influence  the  birth  weight  of  pigs  and  cause  other  varia- 
tions in  connection  with  farrowing.  Influences  may  so  completely 
overlap  one  another  that  in  some  cases  it  is  almost  impossible  to 
account  for  the  variations  which  occur.  However,  the  possible  in- 
fluences considered  in  this  study,  and  which  will  be  taken  up  in  the 
order  named,  are  as  follows:  (1)  length  of  gestation  period;  (2) 
size  of  litter;  (3)  age  of  dam;  (4)  breed;  (5)  time  of  year;  (6) 
order  of  farrowing;  (7)  succeeding  litters  from  the -same  sow. 


The  gestation  period  for  sows  is  generally  considered  to  be  from 
112  to  114  days,  with  a  popular  belief  that  the  older  sows  will  carry 
their  litters  from  one  to  three  days  longer  than  will  the  gilts.  Table 
1  shows  the  relation  of  the  age  of  the  dam  to  the  length  of  gestation 
period  for  549  litters. 

Judging  from  these  data,  the  general  belief  that  older  sows  have 
a  gestation  period  one  to  three  days  longer  than  younger  sows  seems 
to  have  no  very  good  basis;  in  fact,  the  one-year-old  sows  carried 
their  pigs  slightly  longer  than  the  average  for  the  549  litters  from 
Sows  of  all  ages,  which  was  114.58  days  from  the  time  of  service. 
However,  it  is  perhaps  worth  noting  that  the  average  age  of  all  sows 
farrowing  with  gestation*  periods  of  114  days  or  less  was  2.24  years, 
while  that  of  the  sows  which  carried  their  litters  115  days  or  longer 
was  2.31  years ;  which  indicates  that  there  may  be  a  slight  variation 
due  to  age.  Also,  many  of  the  sows  four  years  old  or  above  had 
noticeably  longer  gestation  periods  than  the  average,  but  there  were 
so  few  litters  under  observation  among  the  very  old  sows  that  these 
differences  are  of  doubtful  significance. 

A  variation  of  twenty-six  days  in  the  length  of  gestation  is  some- 
what longer  than  is  expected.  However,  the  fact  that  93.6  percent 


19SO]  VARIATIONS  IN  FAKROW  69 

of  the  litters  were  farrowed  between  the  lllth  and  119th  days  after 
being  bred  indicates  that  the  extreme  cases  shown  in  the  table  are 
riot  duplicated  with  very  great  frequency.  A  further  study  of  the 
same  distribution  indicates  that  the  date  of  farrow  can  be  predicted 
with  but  reasonable  accuracy  since  73.8  percent  of  the  litters  were 
carried  by  the  sows  for  periods  varying  from  113  to  117  days.  Less 
than  20  percent  of  the  litters  were  farrowed  on  the  114th  day,  which 
was  the  day  of  greatest  frequency  of  farrow. 

Table  2  shows  the  relation  of  the  size  of  litter  to  the  length  of 
gestation  for  the  same  549  litters  which  are  shown  in  Table  1.  From 
this  it  seems  that  there  is  a  tendency  for  some  of  the  litters  which 
are  carried  longer  than  the  average  to  be  smaller  than  would 
be  found  in  a  chance  distribution.  This  is  perhaps  more  clearly 
brought  out  in  Table  3,  which  shows  that  the  average  number  of 
pigs  (7.6)  farrowed  in  gestation  periods  longer  than  the  average 
was  less  than  the  grand  average  number  of  pigs  (8.00)  per  litter  in 
466  litters. 

Table  4  shows  a  very  even  distribution  of  pigs  of  the  various  birth 
weights  according  to  the  length  of  the  gestation  period.  The  heav- 
iest pig  in  the  whole  population  of  4,115  pigs  studied  (4.9  pounds) 
was  farrowed  in  a  litter  of  the  shortest  gestation  period  (98  days), 
but  this  pig  seemed  to  stand  out  alone,  there  being  none  other  nearly 
so  heavy.  The  lightest  pig  which  was  farrowed  (0.2  pound)  came 
in  one  of  the  litters  farrowed  on  the  115th  day,  or  near  the  average 
for  the  length  of  gestation.  Aside  from  the  two  pigs  to  which  ref- 
erence has  just  been  made,  and  perhaps  four  or  five  others,  none  of 
which  are  outside  of  a  distribution  such  as  one  would  expect  to  find, 
the  4,115  pigs  on  which  the  individual  weight  as  well  as  the  length 
of  gestation  period  was  secured  are  very  evenly  centered  about  the 
114-  to  115-day  gestation  period  and  the  2.5  pounds  weight  per  pig. 

The  distribution  of  5,188  pigs  as  to  individual  weight,  which  is 
the  number  regarding  which  individual  weights  were  secured,  is 
given  in  the  graph  shown  on  page  70.  This  shows  a  variation 
from  0.2  pound  to  4.9  pounds,  with  a  grand  average  or  mean  weight 
of  2.55  pounds  and  with  66.9  percent  of  the  pigs  weighing  between 
two  and  three  pounds.  It  will  be  noted  that  the  greatest  number 
of  pigs  usually  occurs  at  the  pound  and  half-pound  frequencies. 
This  is  doubtless  due  to  the  fact  that  the  scales  were  graduated  by 
pounds  and  tenths  and  the  pounds  and  half-pounds  were  more  clearly 
marked  than  the  other  divisions,  thus  making  it  more  natural  thai 
the  nearest  pound  or  half-pound  should  be  read.  It  is  doubtful,  how- 
ever, whether  this  error  would  noticeably  alter  the  true  average 
weight  of  the  whole  population,  the  inequalities  probably  balancing 
one  another. 


70 


BULLETIN  No.  226 


[May, 


42 


G  1.4  1.5 


1920}  VARIATIONS  IN  FARROW  71 

A  study  of  the  litters  as  regards  the  relation  of  breed  to 
the  length  of  gestation  period  (Table  5)  reveals  the  fact  that  two 
breeds,  Berkshire  and  Poland  China,  stand  out  alone  as  having 
longer  gestation  periods  than  the  average  for  the  549  litters.  The 
Poland  Chinas  carried  their  pigs  an  inappreciable  fraction  of  a  day 
longer  than  the  grand  average,  but  the  Berkshires  ran  over  more 
than  three-fourths  of  a  day.  The  fact  that  the  Berkshires  seem  to 
have  longer  normal  gestation  periods  than  any  other  breed  involved 
in  this  study,  together  with  the  fact  that  there  were  more  Berkshire 
litters  studied  than  litters  of  all  other  breeds  combined,  explains  in 
part  the  reason  for  the  grand  average  gestation  period  under  con- 
sideration being  somewhat  longer  in  these  549  litters  than  is  gen- 
erally considered  to  be  normal.  Outside  of  the  Hampshires,  of  which 
there  were  but  two  litters,  the  Chester  Whites  had  the  shortest 
average  gestation  period.  Following  these  in  order  of  increasing 
gestation  period  are  the  Duroc-Jerseys,  Large  Yorkshires,  Tarn- 
worths,  Poland  Chinas,  and  Berkshires. 

A  study  of  the  sex  of  the  pigs  in  relation  to  the  length  of  gesta- 
tion period  (Table  6)  shows  no  apparent  tendency  for  either  sex  to 
predominate  more  than  normal.  In  a  majority  of  cases  there  were 
more  males  than  females.  Of  the  4,363  pigs  on  which  the  sex  as 
well  as  the  gestation  period  was  recorded,  2,074  were  females  and 
2,289  males,  or  47.5  percent  females  and  52.5  percent  males. 

Table  7,  showing  the  sex  of  the  first  and  last  born  according 
to  length  of  gestation  period,  indicates  that  there  is  possibly  a 
tendency  for  males  to  predominate  among  the  first  farrowed  in  any 
given  litter,  and  for  the  sex  to  be  rather  evenly  distributed  in  the 
case  of  the  last  farrowed.  However,  from  this  table  it  is  seen  that 
in  litters  farrowed  on  the  114th  day,  females  predominated  among 
both  the  first  and  last  farrowed,  notwithstanding  the  fact  that  there 
were  more  males  than  females  among  the  total  number  farrowed. 
The  study  of  the  sex  of  the  first  and  last  farrowed  involves  so  few 
individuals  that  no  definite  conclusions  can  be  drawn. 

SIZE  OF  LITTER 

The  number  of  pigs  per  litter  was  obtained  in  connection  with 
each  of  720  litters  containing  a  total  of  5,840  pigs.  Table  8  shows 
the  sex  of  these  pigs  as  they  varied  within  litters  of  different  sizes. 
Altho  there  were  183  pigs  the  sex  of  which  was  not  obtained,  a  sex 
distribution  of  the  remaining  5,657  is  interesting  and  seems  to  in- 
dicate that  there  is  a  decided  tendency  for  males  to  predominate, 
since  of  this  number  2,933  were  males  and  only  2,724  were  females, 
or  51.9  percent  males  and  48.1  percent  females.  There  seemed  to  be 
no  noticeable  correlation  between  the  size  of  the  litter  and  sex,  a 


72  BULLETIN  No.  226  [May, 

predominance  of  males  being  found  in  a  majority  of  different-sized 
litters  rather  than  merely  a  tendency  for  this  sex  to  predominate  in 
those  of  certain  sizes,  either  small  or  large. 

Table  9,  showing  the  number  of  pigs  farrowed  dead  or  immature 
in  the  litters  of  different  sizes,  seems  to  indicate  that  there  is  a 
tendency  for  the  larger  litters  to  contain  a  larger  proportion  of 
dead  or  immature  pigs  than  are  found  in  the  smaller  litters,  since  in 
litters  of  eight  pigs  or  less  the  percentage  of  dead  or  immature  at 
birth  was  7.7,  whereas  in  the  litters  of  more  than  eight  pigs,  10.5 
percent  is  the  corresponding  figure.  Among  those  farrowed  dead 
there  was  a  greater  proportion  of  males  than  females — 56.0  percent 
males  and  44.0  percent  females,  which  is  a  significant  difference. 

A  study  of  the  distribution  of  5,774  pigs  according  to  the  size 
of  the  litter  as  well  as  the  age  of  dam,  as  given  in  Table  10,  indicates 
that  sows  under  two  years  of  age  produce  smaller  litters  than  do 
sows  two  to  four  years  of  age.  The  line  of  averages  at  the  bottom 
of  the  table  shows  a  gradual  increase  in  the  size  of  litter  as  the  sows 
grew  older  up  to  the  time  that  they  were  three  years  old.  After 
the  sows  had  attained  the  age  of  three  years  they  had  a  tendency 
to  produce  fewer  pigs  in  each  succeeding  litter,  altho  the  few  sows 
which  were  kept  until  they  were  over  five  years  of  age  seemed  to 
maintain  their  fecundity  better  than  the  average  even  at  younger 
ages.  There  was,  however,  at  least  one  force  operating  in  the  herd 
which  would  tend  to  maintain  or  possibly  increase  the  size  of  litter ; 
namely,  the  fact  that  no  sows  were  retained  in  the  breeding  herd 
unless  they  proved  to  be  producers  either  of  large  litters  or  of  litters 
containing  pigs  of  special  worth.  As  a  result  of  this  selection  some 
of  the  gilts  which  produced  small  litters  were  discarded  and  did 
not  have  an  opportunity  to  exert  an  influence  as  older  sows.  On 
the  other  hand,  this  sort  of  selection  is  just  what  would  probably 
be  made  in  any  herd,  and  the  results  here  are  therefore  somewhat 
comparable  to  those  which  might  generally  be  found. 

The  distribution  of  2,483  sow  pigs  showing  the  relation  of  the 
weights  of  the  pigs  to  the  size  of  the  litter  in  which  they  were  far- 
rowed (Table  11),  as  well  as  a  similar  distribution  for  the  2,705 
boar  pigs  on  which  the  individual  weights  at  farrowing  time  were 
secured  (Table  12),  shows  a  marked  regularity  in  centering  around 
the  averages.  The  succeeding  table  (Table  13)  shows  the  same  data 
in  a  form  which  may  be  more  easily  studied.  In  these  comparisons 
the  average  weight  of  the  2,483  sow  pigs  is  shown  as  2.51  pounds 
and  that  of  the  2,705  boar  pigs  as  2.59  pounds,  the  males  being 
heavier  by  0.08  pound.  A  study  of  the  average  weight  of  all  pigs 
farrowed  in  litters  of  different  sizes  shows  rather  clearly  that  in 
litters  smaller  than  the  average  (8.0  pigs)  the  average  weight  per 
pig  (2.67  pounds)  is  likely  to  be  greater  than  the  grand  average 


1920]  VARIATIONS  IN  FARROW  73 

weight  for  all  litters  (2.55  pounds  for  the  5,188  pigs  on  which  the 
individual  weights  were  obtained).  Those  farrowed  in  litters  of 
more  than  eight  pigs  weighed  an  average  of  2.47  pounds  each.  In 
every  case  where  the  litter  contained  more  pigs  than  the  average, 
the  average  weight  of  all  pigs  in  litters  of  that  size  was  noticeably 
less  than  the  grand  average.  Making  a  similar  comparison  by  sex, 
we  find  that  likewise  the  pigs  of  either  sex  in  litters  larger  than 
the  average  have  a  tendency  to  be  lighter  than  the  average  for  pigs 
of  that  sex,  and  in  litters  smaller  than  the  average  the  tendency  is 
for  the  pigs  to  be  heavier  than  the  average  for  that  sex. 

.  AGE  OF  DAM 

Sows  which  are  two  years  old  or  older  are  generally  considered 
to  be  producers  of  larger  litters  and  stronger  pigs  than  are  gilts  or 
sows  one  and  one-half  years  old. 

Table  14,  showing  the  relation  of  the  age  of  the  dam  to  the  birth 
weight  of  the  pigs,  indicates  rather  clearly  that  the  young  sowjs 
farrow  noticeably  lighter  pigs  than  do  the  older  mothers.  The 
average  weight  of  pigs  from  sows  under  two  years  of  age  was  2.44 
pounds,  as  compared  with  an  average  weight  of  2.61  pounds  for 
the  pigs  from  sows  two  years  old  and  older.  There  seemed  to  be 
a  fairly  general  increase  in  the  weight  of  the  pigs  as  the  sows  grew 
older,  even  until  they  were  eight  years  old,  altho  there  were  so  few 
sows  over  five  years  that  the  weight  of  the  pigs  from  sows  past 
maturity  may  not  be  representative.  On  the  whole,  however,  the 
belief  that  the  young  sows  produce  smaller  pigs  is  substantiated  by 
these  data.  Table  10,  given  in  connection  with  the  discussion  on 
the  size  of  litters,  likewise  substantiates  the  popular  belief  that 
up  to  a  certain  age,  which  is  about  three  years,  there  is  an  increase 
in  the  size  of  litters  as  the  sow  grows  older. 

One  frequently  hears  statements  to  the  effect  that  even  tho  the 
older  sows  farrow  larger  litters  than  the  gilts,  they  do  not  raise  as 
large  a  percentage  of  the  pigs  farrowed  because  more  of  them  are 
farrowed  weak  or  dead.  Table  15,  in  which  the  number  of  dead  or 
immature  pigs  is  given  in  litters  from  sows  of  different  ages,  shows 
that  the  old  sows  farrowed  a  greater  percentage  of  dead  pigs  than 
did  young  dams.  Eight  and  one-tenth  percent  of  the  pigs  farrowed 
by  sows  under  three  years  of  age  were  dead  or  immature,  whereas 
12.3  percent  (an  increase  of  4.2  percent)  of  those  from  dams  three 
years  or  more  in  age  were  in  similar  condition  at  birth.  There  was, 
however,  marked  irregularity  among  the  proportionate  number  ofr 
dead  or  immature  at  birth  among  the  litters  from  sows  three  years 
old  and  over.  There  were  also  few  litters  of  these  classes. 

The  sex  of  pigs  in  litters  from  sows  of  different  ages  (Table  16) 
is  about  as  evenly  distributed  as  it  was  in  litters  of  different  sizes 


74  BULLETIN  No.  226  [May, 

(Table  8)  or  in  litters  of  different  lengths  of  gestation  (Table  6). 
It  shows  a  uniform  tendency  for  males  to  be  present  in  slightly 
greater  numbers  than  are  the  females. 

BREED 

Any  study  which  can  be  made  of  the  different  breeds  from  the 
data  available  in  this  research  cannot  be  conclusive  because  for 
accurate  comparisons  there  have  been  too  few  litters  from  any  one 
breed,  with  the  possible  exception  of  the  Berkshires.  At  best,  breed 
comparisons  of  any  kind  are  of  doubtful  value  and  are  dangerous 
indulgences.  However,  these  data  were  collected  and  are  given  here 
as  a  possible  supplement  to  any  other  which  may  be  available  at 
present  or  obtained  at  any  future  time.  Table  17  shows  the  total 
number  of  litters  of  each  breed  in  the  720  litters  under  observation. 
From  this  table  it  is  evident  that  more  Berkshire  litters  were  far- 
rowed in  the  herd  during  the  years  that  these  data  were  being  col- 
lected (1903-1916)  than  all  other  breeds  combined. 

The  compilation  showing  by  breeds  the  average  age  of  sows, 
the  average  length  of  gestation  period,  the  number  of  pigs  per 
litter,  and  the  average  weight  per  pig  at  farrowing,  as  pre- 
sented in  Table  18,  gives  an  opportunity  for  comparison  of  breeds, 
so  far  as  the  available  material  herein  presented  will  permit.  (All 
litters  of  which  the  breeding  was  not  definitely  known  or  concern- 
ing which  there  was  any  doubt  were  omitted.) 

The  average  age  of  the  sows  at  the  time  the  litters  were  farrowed 
did  not  vary  widely,  there  being  some  sows  of  each  breed  that  were 
kept  until  they  were  four  or  five  years  old ;  consequently  any  varia- 
tion which  may  be  found  cannot  logically  be  explained  by  variations 
in  age. 

In  the  discussion  in  connection  with  Table  5  the  variation  in 
length  of  gestation  was  considered,  and  therefore  will  not  be  re- 
peated here. 

The  largest  variation  which  was  found  among  the  litters  of  the 
different  breeds  was  in  the  size  of  litters,  altho  there  was  some  no- 
ticeable variation  in  the  weight  of  the  pigs.  Arranging  the  breeds 
according  to  the  descending  number  of  pigs  per  litter,  as  well  as 
the  descending  weight  per  pig,  we  have  the  following : 

Pigs  per  litter  Weight  per  pig 

Large  Yorkshire 11.58  Berkshire    2.61 

Chester  White   9.59  Large  Yorkshire 2.60 

Tamworth 9.43  Chester  White 2.59 

Duroc-Jersey    8.74  Tamworth 2.58 

Crossbred 8.00  Poland  China 2.50 

Berkshire    7.42  Hampshire    2.50 

Hampshire    7.00  Crossbred 2.46 

Poland  China 6.57  Duroc-Jersey    2.25 

Average 8.00  Average 2.53 


VARIATIONS  IN  FARROW  75 

In  this  at  first  there  seems  to  be  some  evidence,  which  is  con- 
tradictory to  that  found  in  the  study  of  the  size  of  the  litters  and 
its  effect  on  the  weight  of  the  pigs,  for  the  Large  Yorkshire  litters, 
altho  they  contained  more  pigs  as  an  average  than  the  average  for 
litters,  were  composed  of  pigs  which  were  heavier  than  the  average. 
A  similar  statement  is  also  true  of  the  Chester  White  and  Tamworth 
pigs.  Contrary  to  this,  we  find  that  the  Hampshire  and  Poland 
China  litters,  with  fewer  pigs  than  the  average,  had  lighter  pigs  than 
the  mean  of  the  whole  population.  Further,  it  is  to  be  noted  that 
the  Duroc-Jersey  pigs  weighed  over  one-fourth  pound  (0.28  pound) 
less  than  the  average  for  all  pigs.  Such  findings  are  a  concrete 
illustration  of  the  differences  due  to  breeding. 

The  foregoing  tabulation  shows  the  results  of  but  457  litters,  the 
litters  containing  a  total  of  3,658  pigs,  an  average  of  8.00  individuals 
per  litter.  The  sows  averaged  2.35  years  in  age. 

TIME  OF  YEAR 

The  time  of  the  year  at  which  pigs  are  farrowed  does  not 
seem  to  exert  any  very  noticeable  influence,  with  any  regularity, 
upon  the  length  of  gestation  period,  size  of  litter,  or  weight  of  pigs, 
altho  possibly  there  is  a  tendency  for  larger  litters  and  heavier  pigs 
to  occur  in  the  months  of  normal  farrowing  seasons.  This,  of 
course,  might  be  expected  since  sows  farrowing  in  other  months 
are,  in  many  cases,  ones  which  were  re-bred,  having  been  originally 
bred  for  the  normal  farrowing  season.  Such  sows  are  doubtless 
somewhat  abnormal.  There  are  no  positive  indications  that  the  sows 
will  carry  their  litters  longer  during  summer  months  than  in  winter, 
or  vice  versa.  Summarizing  here  the  data  presented  in  Table  19,  and 
arranging  it  by  months  in  descending  order,  we  have : 

.          ,  Length  of  gestation  Pigs  per  Weight 

period  litter  per  pig 


July  September  October  July 

April  May  August  September 

March  February  April  August 

September  March  March  October 

October  June  February  February 

August  October  September  April 

June  April  '        May  March 

May  July  June  May 

February  November  July  November 

November  August  November  June 

ORDER  OF  FARROWING  , 

Table  20,  showing  the  relation  of  order  of  farrowing  to  sex  and 

weight  of  pigs  in  the  261  litters  on  which  the  order  of  farrowing 
as  well  as  the  birthweight  of  all  the  pigs  in  the  litters  was  ob- 


76  BULLETIN  No.  226 

tained,  indicates  rather  strongly  that  among  the  first  farrowed,  males 
tend  to  predominate  more  than  normal,  for  there  were  155  males  to 
106  females  among  the  first  born.  The  sex  of  the  last  farrowed  was 
in  about  the  normal  ratio. 

The  same  table  also  indicates  that  there  is  a  slight  tendency  for 
the  first  farrowed  (average  weight  2.60  pounds)  to  be  heavier  than 
the  last  farrowed  (average  weight  2.43  pounds).  This  is  perhaps 
in  part  due  to  the  predisposition  of  the  males,  which  predominated 
here,  to  be  heavier  than  the  females.  In  the  case  of  the  first  far- 
rowed here,  the  males  averaged  2.67  pounds  and  the  females  only 
2.50  pounds.  There  was  a  somewhat  similar  tendency  for  the  males 
to  predominate  and  to  be  somewhat  heavier  than  the  females,  among 
the  last  farrowed,  but  the  tendency  was  not  so  marked  as  among 
the  first  farrowed. 

SUCCEEDING  LITTERS  FROM  THE  SAME  SOW 

In  Table  21  is  shown  the  average  age,  length  of  gestation  period, 
number  of  pigs  per  litter,  and  weight  of  litter  and  pigs  in  succeding 
litters  from  the  same  sow. 

The  gestation  period  of  the  first  litter  is  rather  consistently 
longer  than  for  those  following  it,  as  was  shown  in  Table  1.  There 
is  an  increase  in  the  number  of  pigs  per  litter  in  most  cases  until 
the  fourth  litter,  at  which  time  the  sows  are  three  to  three  and  one- 
half  years  old.  The  total  weight  of  the  litter  increases  with  each 
succeeding  litter  up  to  the  fourth  owing  to  the  increase  in  the  num- 
ber of  pigs  per  litter  as  well  as  in  the  weight  of  the  individual  pigs. 

The  age  at  which  a  sow  should  farrow  her  first  litter,  as  well  as 
the  optimum  frequency  of  succeeding  litters,  is  a  much  debated 
subject.  No  positive  conclusions  can  be  drawn  from  Table  22,  which 
gives  the  succeeding  litters  from  the  same  sows  at  different  ages, 
for  there  are  doubtless  other  factors  than  those  in  the  table  which 
should  be  taken  into  consideration  in  determining  the  age  at  which 
a  sow  should  farrow.  One  would  infer  from  the  first  part  of  the 
table  that  sows  farrowed  their  first  litters  at  one  and  one-half  years 
of  age  had  shorter  gestation  periods  and  farrowed  more  and  heavier 
pigs  than  sows  that  farrowed  their  first  litters  at  one  year  of  age. 
Upon  studying  other  parts  of  the  table,  it  is  readily  seen  that  con- 
flicting conclusions  can  be  drawn.  The  sows  that  farrowed  their 
first  litters  at  one  and  one-half  years  of  age  rather  consistently 
farrowed  heavier  pigs  in  the  first  litter  than  those  which  farrowed 
at  one  year.  It  is  evident  that  other  factors  than  the  number  of 
pigs  and  their  size  determine  the  age  at  which  sows  should  farrow 
the  first  and  succeeding  litters  for  maximum  or  economical 
production. 


19SO]  VARIATIONS  IN  FARROW  .    77 


The  data  presented  in  this  study  are  not  of  sufficient  extent  to 
warrant  the  drawing  of  many  final  conclusions.  A  few  seem  to  be 
justified,  however,  and  are  given  here  in  the  summary,  altho  it  must 
be  borne  in  mind  that  even  they  are  based  on  limited  data. 

LENGTH  OF  GESTATION  PERIOD. — The  records  obtained  from  549 
litters  showed  a  rather  wide  range,  98  to  124  days,  in  the  length  of 
gestation  period,  with  an  average  of  114.58  days.  However,  93.6 
percent  of  the  litters  were  farrowed  between  the  lllth  and  119th 
days,  and  73.8  percent  between  the  113th  and  117th  days. 

Altho  there  may  be  a  slight  variation  in  length  of  gestation  period 
due  to  age,  the  general  belief  that  older  sows  have  a  gestation  period 
one  to  three  days  longer  than  younger  sows  seems  to  have  no  very 
good  basis. 

There  was  little,  if  any,  correlation  between  the  length  of  gesta- 
tion period  and  the  birth  weight  of  pigs,  but  there  was  a  slight  tendency 
for  some  of  the  litters  which  were  carried  longer  than  the  average  to 
be  smaller  than  those  which  were  farrowed  earlier  than  the  average. 

A  study  of  the  sex  of  the  pigs  in  relation  to  the  length  of  gesta- 
tion period  shows  no  apparent  tendency  for  either  sex  to  predominate 
more  than  normal. 

SIZE  OF  LITTER. — In  this  study  the  average  size  of  litter  was  8.1 
pigs.  The  average  weight  of  a  litter  is  about  20  pounds.  This 
weight  varies  almost  in  direct  proportion  to  the  number  of  pigs  in 
the  litter.  In  litters  with  fewer  pigs  than  the  average,  the  average 
weight  of  pigs  is  greater  than  in  litters  with  more  pigs  than  the 
average.  In  this  study,  the  average  weight  of  pigs  in  litters  with 
fewer  pigs  than  the  average  was  2.67  pounds,  and  in  litters  with 
more  pigs  than  the  average  it  was  2.47  pounds,  while  the  grand 
average  of  all  pigs  was  2.55  pounds. 

There  is  no  noticeable  correlation  between  size  of  litter  and  sex. 
It  is  interesting  to  note,  however,  that  among  a  total  of  5,657  pigs, 
the  sex  of  which  was  determined,  51.9  percent  were  males  and  48.1 
percent  females.  The  predominance  of  males  was  found  in  a  majority 
of  different-sized  litters  rather  than  in  those  of  certain  sizes,  either 
large  or  small. 

There  is  a  tendency  for  the  larger  litters  to  contain  a  larger  pro- 
portion of  dead  or  immature  pigs  than  are  found  in  the  smaller 
litters.  The  litters  larger  than  the  average  contained  10.5  percent 
dead  pigs,  and  the  litters  smaller  than  the  average,  7.7  percent.  The 
proportion  of  males  (56.0  percent)  among  those  farrowed  dead  was 
greater  than  the  normal  predominance  of  males  over  females.  The 


78  BULLETIN  No.  226  [May, 

pigs  farrowed  dead  or  immature  were  decidedly  lighter  (2.17  pounds) 
than  the  total  average  weight  per  pig  (2.55  pounds). 

AGE  OF  DAM. — On  the  whole,  the  belief  that  young  sows  produce 
smaller  pigs  than  do  older  sows  is  substantiated  by  these  data.  Like- 
wise the  data  substantiate  the  popular  belief  that  up  to  a  certain  age, 
which  is  about  three  years,  there  is  an  increase  in  the  size  of  litter 
as  the  sows  grow  older.  In  this  study  the  average  number  of  pigs 
from  sows  one  and  one  and  one-half  years  old  was  7.5,  and  from  sows 
two  years  old  or  older  8.6,  with  average  weights  of  2.44  pounds  and 
2.61  pounds  respectively. 

The  older  sows  farrowed  a  greater  percentage  of  dead  or  imma- 
ture pigs  than  did  the  younger  sows.  Out  of  a  total  of  5,778  pigs, 
8.1  percent  of  those  farrowed  by  sows  one  to  two  and  one-half  years 
old  were  dead  or  immature,  while  12.3  percent  of  those  farrowed  by 
sows  three  years  old  or  over  were  farrowed  dead  or  immature. 

A  study  of  the  sex  of  pigs  from  sows  of  different  ages  showed  a 
uniform  tendency  for  males  to  be  present  in  slightly  greater. numbers 
without  relation  to  the  age  of  the  sow. 

BREED. — There  are  rather  wide  differences  among  different  breeds 
as  to  the  length  of  gestation,  size  of  litter,  and  birth  weight  of  pigs. 
Berkshires  had  appreciably  longer  gestation  periods  (115.4  days) 
than  did  any  of  the  other  breeds. 

TIME  OF  YEAR. — It  is  very  doubtful  whether  there  are  any  varia- 
tions in  farrow  which  can  be  attributed  to  the  season  at  which  the 
pigs  are  farrowed. 

ORDER  OF  FARROWING. — Of  the  first  farrowed,  the  proportion  of 
males  (59.4  percent)  was  greater  than  the  normal  ratio  of  males  to 
females.  The  sex  of  the  last  farrowed  (51.0  percent  males)  was  in 
about  the  normal  ratio.  In  comparing  the  averages  of  the  same  sex, 
as  well  as  the  averages  of  both  sexes,  it  was  found  that  the  average 
weight  of  the  first  farrowed  was  somewhat  heavier  than  the  average 
of  the  last  farrowed. 

SUCCEEDING  LITTERS  FROM  THE  SAME  Sow. — There  was  an  increase 
in  the  number  of  pigs  per  litter  and  in  the  weight  of  individual  pigs 
in  most  cases  until  the  fourth  litter,  at  which  time  the  sows  were  three 
to  three  and  one-half  years  old.  The  data  compiled  in  an  attempt  to 
throw  light  upon  the  much  debated  subject  of  the  age  at  which  a 
sow  should  farrow  her  first  litter,  as  well  as  the  optimum  frequency 
of  succeeding  litters,  is  decidedly  conflicting.  It  would  seem  that 
other  factors  than  the  number  of  pigs  and  their  size  should  determine 
the  age  at  which  sows  should  farrow  the  first  and  succeeding  litters 
for  maximum  or  economical  production. 


19SSO']  VARIATIONS  IN  FARROW  79 


INDEX  TO  TABLES 

PAGE 

1  Eelation  of  Age  of  Dam  to  Length  of  Gestation  Period 80 

2  Kelation  of  Size  of  Litter  to  Length  of  Gestation  Period 81 

3  Eelation  of  Length  of  Gestation  Period  to : 

(a)  Size  of  Litter 

(b)  Number  of  Pigs  Farrowed  Dead  or  Immature 

(c)  Weight  of  Litter 

(d)  Weight  of  Pigs 82 

4  Eelation  of  Length  of  Gestation  Period  to  Birth  Weights  of  Pigs 83 

5  Eelation  of  Breed  to  Length  of  Gestation  Period 84 

6  Eelation  of  Length  of  Gestation  Period  to  Sex  of  Pigs 85 

7  Eelation  of  Length  of  Gestation  Period  to  Sex  of  Pigs  Farrowed  First 

and  Last  in  the  Litter 85 

8  Eelation  of  Size  of  Litter  to  Sex  of  Pigs 86 

9  Eelation  of  Size  of  Litter  to  Number  of  Pigs  Farrowed  Dead  or  Immature .   86 

10  Eelation  of  Size  of  Litter  to  Age  of  Dam 87 

11  Eelation   of   Weight    of   Pigs    to    Size    of   Litter    in   Which   Farrowed: 

Females 88 

12  Eelation  of  Weight  of  Pigs  to  Size  of  Litter  in  Which  Farrowed :  Males       89 

13  Eelation  of  Weight  of  Pigs  to  Size  of  Litter  in  Which  Farrowed:     Males 

and  Females    90 

14  Eelation  of  Age  of  Dam  to  Birth  Weight  of  Pigs 90 

15  Eelation  of  Age  of  Dam  to  Number  of  Pigs  Farrowed  Dead  or  Immature.  91 

16  Eelation  of  Age  of  Dam  to  Sex  of  Pigs 91 

17  Total  Number  of  Litters  of  Each  Breed 91 

18  Eelation  of  Breeding  to: 

(a)  Age  of  Dam 

(b)  Length  of  Gestation  Period 

(c)  Size  of  Litter 

(d)  Weight  of  Litter 

(e)  Weight  of  Pigs 92 

19  Eelation  of  Month  of  Farrowing  to: 

(a)  Age  of  Dam 

(b)  Length  of  Gestation  Period 

(c)  Size  of  Litter 

(d)  Weight  of  Litter 

(e)  Weight   of  Pigs 92 

20  Eelation  of  Order  of  Farrowing  to  Sex  and  Weights  of  Pigs 93 

21  Data  Concerning  Succeeding  Litters  from  the  Same  Sows 94 

22  Data  Concerning  Succeeding  Litters  from  the  Same  Sows  at  Different 

Ages 95 


SO 


BULLETIN  No.  226 


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BULLETIN  No.  226 


[May, 


TABLE  3. — RELATION  OP  LENGTH  OP  GESTATION  PERIOD  TO:    (a)  SIZE  OP 

LITTER,  (b)  NUMBER  OP  PIGS  FARROWED  DEAD  OR  IMMATURE, 

(c)  WEIGHT  OP  LITTER,  AND  (d)  WEIGHT  OP  PIGS 


Length  of 
gestation 
period, 

days 

Num- 
ber of 
litters 

Total 
number 
of 
pigs 

Average 
number 
of  pigs 
per 
litter 

Pigs  farrowed 
dead  or  immature 

Average 
weight 
per 
litter, 
Ibs. 

Average 
weight 
per  pig, 

Ibs. 

Number 

Percent 

98.. 

2 
1 
1 
3 
3 
2 
10 
13 
39 
60 
88 
80 
84 
42 
23 
8 
3 
2 
1 
1 

16 
9 
10 
27 
16 
15 
71 
112 
329 
544 
725 
611 
648 
338 
157 
63 
24 
5 
10 
9 

8.0 
9.0 
10.0 
9.0 
5.3 
7.5 
7.1 
8.6 
8.4 
9.1 
8.2 
7.6 
7.7 
8.0 
6.8 
7.9 
8.0 
2.5 
10.0 
9.0 

'i 

1 

'3 
13 
7 
25 
37 
57 
45 
45 
23 
19 
4 
1 

io!6 

3.7 

26!6 
18.3 
6.3 
7.6 
6.8 
7.9 
7.4 
6.9 
6.8 
12.1 
6.3 
4.2 

26.1 
20.4 
27.9 
20.6 
13.8 
18.8 
17.4 
21.4 
21.2 
22.8 
20.3 
19.7 
19.8 
20.5 
18.5 
21.1 
18.2 
7.9 
22.4 
20.2 

3.26 
2.27 
2.79 
2.29 
2.58 
2.51 
2.45 
2.48 
2.51 
2.51 
2.46 
2.59 
2.57 
2.55 
2.71 
2.68 
2.28 
3.14 
2.24 
2.24 

102  

103  

106  

107  

108  

110  

Ill  

112  

113  

114  

115  

116  

117  

118  

119  

120  

121  

123  

124  

Total  or  average.  . 

466 

3739 

8.0 

281 

7.5 

20.3 

2.54 

Farrowed     on     or 
before  the  114th 
day  

222 
244 

1874 
1865 

8.4 
7.6 

144 
137 

7.7 
7.3 

21.0 
19.7 

2.49 

2.58 

Farrowed  after  the 
114th  day  

19X0} 


VARIATIONS  IN  FARROW 


83 


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84 


BULLETIN  No.  226 


[May, 


£ 

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« 

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1920] 


VARIATIONS  IN  FARROW 


85 


TABLE  6. — RELATION  OP  LENGTH  OF  GESTATION  PERIOD  TO  SEX  OF  PIGS 


Length  of  gestation 
period, 

days 

Sex  of  pigs 

Number  of  pigs  in 
these  litters,  sex  of 
which  was  not 
obtained 

Total  number 
of  pigs 
studied 

Female 

Male 

98..  . 

10 
4 
3 
10 
6 
9 
34 
59 
177 
314 
427 
339 
334 
202 
81 
36 
15 
3 
3 
8 

6 
5 
7 
17 
10 
6 
46 
81 
210 
298 
446 
370 
404 
211 
106 
35 
14 
2 
9 
6 

ie> 

4 
4 
9 
17 
6 
24 
15 
9 
1 
3 

'e 

16 
9 
10 
27 
16 
15 
96 
156 
391 
621 
890 
715 
762 
428 
196 
72 
32 
5 
18 
14 

102   

103  

106  

107       

108  

110  

Ill  

112  

113  

114  

115  

116  

117  

118  

119  

120  

121  

123  

124  

Total  

2074 
45 

2289 
63 

114 

4477 

Percent  

47.5 

52.5 

Number  farrowed  on  or  be- 
fore the  114th  day  

1053 
1021 

1132 
1157 

50 
64 

2235 
2242 

Number  farrowed  after  the 
114th  day  

TABLE  7. — RELATION  OF  LENGTH  OF  GESTATION  PERIOD  TO  SEX  OF  PIGS 
FARROWED  FIRST  AND  LAST  IN  THE  LiTTER1 


Length  of 
gestation  period, 
days 

FIRST  FABBOWED 

LAST  FARROWED 

Sows 

Boars 

Sows 

Boars 

106.  .  . 

1 

'4 
12 
13 
29 
15 
19 
12 

a 

2 

'i 

1 

'5 
4 
8 
16 
19 
31 
30 
11 
9 
1 
2 
1 
2 
1 

1 
1 
1 

'i 

3 
9 
17 
25 
18 
22 
4 
4 
1 
2 
1 

'4 
4 
10 
10 
15 
24 
19 
17 
10 
1 

'i 

1 

107  

108  

109  

110  

111  

112  

113  

114  

115  

116  

117  

118  

119  

120  

121  

123  

124  

Total  

112 

142 

110 

116 

Percent  of  each  sex  .... 

44.1 

55.9 

48.7 

51.3 

Number  farrowed  on  or 
before  the  114th  day..  . 
Number  farrowed  after 
the  114th  dav... 

59 
53 

54 
88 

58 
52 

43            ' 
73 

'In  some  cases  the  sex  of  the  last  farrowed  was  not  secured,  owing  either  to  absence  of  attend- 
ant or  to  the  fact  that  it  was  not  possible  to  determine  the  sex. 


86 


BULLETIN  No.  226 


[May, 


TABLE  8. — RELATION  OF  SIZE  OF  LITTER  TO  SEX  OF  PIGS 


Number  of  pigs 
per  litter 

Number  of  pigs  of 
each  sex 

Number  ofpigs, 
sex  of  which 
was  not  obtained 

Total  number 
studied 

Females 

Males 

I... 

2 
15 
30 
97 
137 
195 
255 
374 
331 
449 
292 
237 
149 
101 
29 
11 
8 
12 

4 
15 
27 
82 
157 
213 
347 
397 
329 
442 
326 
226 
179 
105 
45 
21        ' 
10 
8 

'i 
11 

12 
21 
13 
24 
19 
20 
17 
10 
18 
1 
16 

6 
30 

57 
180 
305 
420 
623 
784 
684 
910 
638 
480 
338 
224 
75 
48 
18 
20 

2  

3  

4  

5  

6  

7  

8  

9  

10  

11  

12  

13  

14  

15  

16  

18  

20  

Total  

2724 

2933 

183 

5840 

Percent  of  each  sex  

48.1 

51.9 

Number  in  litters  of  8 
pigs  or  less  

1105 
1619 

1242 
1691 

2405 
3435 

Number  in   litters   of   more 
than  8  pigs  

TABLE  9. — RELATION  OF  SIZE  OF  LITTER  TO  NUMBER  OF  PIGS  FARROWED 
DEAD  OR  IMMATURE 


Number  of  pigs 
per  litter 

Pigs  farrowed  dead  or  immature 

Number  of 
litters 

Total 
number 
of  pigs 

Females 

Males 

Totali 

Percent 

1... 

1 

'i 
3 
7 
14 
8 
26 
18 
25 
30 
30 
23 
24 
6 
2 
1 
2 
2 

1 
4 
4 
17 
26 
25 
66 
42 
63 
60 
69 
53 
55 
44 
3 
5 
3 
5 

16.6 
13.3 
7.0 
9.4 
8.5 
6.0 
10.6 
5.4 
9.2 
6.6 
10.8 
11.0 
16.3 
19.6 
4.0 
10.4 
16.7 
25.0 

6 
15 
19 
45 
61 
70 
89 
98 
76 
91 
58 
40 
26 
16 
5 
3 
1 
1 

6 
30 

57 
180 
305 
420 
623 
784 
684 
910 
638 
480 
338 
224 
75 
48 
18 
20 

2  

3  

1 
9 
8 
7 
19 
13 
13 
18 
19 
20 
21 
20 

4  

5  

6  

7  

8  

9  

10  

11  

12  

13  

14  

15  

16  

4 
1 
3 

18  

20  

Total  

177 

225 

5451 

9.3 

720 

5840 

Percent  

44 

56 

Number  in  litters  of  8 
pigs  or  less   . 

58 
119 

80 
145 

185 
360 

7.7 
10.5 

403 
317 

2397 
3435 

Number  in   litters  of 
more  than  8  pigs  

'The  sex  of  some  of  the  dead  pigs  and  of  some  of  those  that  were  immature  was  not  obtained. 
NOTE. — 9.3  percent  of  the  pigs,  or  1.3  pigs  per  litter,  were  farrowed  dead  or  immature.    The 
average  weight  of  the  pigs  farrowed  dead  or  immature  in  720  litters  was  2.17  pounds. 


VARIATIONS  IN  FARROW 


87 


TABLE  10. — RELATION  OF  SIZE  OF  LITTER  TO  AGE  OF  DAM 


Number  of  pigs 
per  litter 

Age  of  dam,  years 

Total 
number 
of 

litters 

1 

1H 

2 

2K 

3 

sy2 

4 

4M 

5 

5H 

6 

6^ 

7 

8 

1           

X 

9 

5 
15 
18 
43 
61 
68 
87 
96 
75 
91 
57 
40 
26 
16 
5 
3 
1 
1 

2 

4 
7 
13 
20 
14 
22 
23 
21 
17 
11 
4 
2 
1 

3 

2 
10 
11 
17 
13 
24 
17 
15 
8 
9 
3 
2 

2 
1 
7 
12 
12 
13 
19 
10 
21 
3 
10 
7 
6 

3 
2 
2 
4 
8 
8 
11 
9 
11 
9 
6 
4 
1 
2 

1 

'"3 

4 
4 
7 
5 
4 
4 
5 
2 

2 

1 

3                      ... 

1 

6 
3 
5 
7 
4 
7 
6 
13 
4 
6 
4 

i 

2 
3 
5 

8 
2 
5 

4 
4 
1 
3 

1 

3 

4 

5 

1 
1 
3 
4 

2 
2 
2 
1 

1 

6 

7  

"i 

1 
2 
1 
3 

1 

1 

1 

8              

g 

1 
1 

10 

6 
1 
1 
1 

2 
2 

1 

i 
i 

2 

11 

12     

13 

14 

1 

15  

3 

16   

1 

1 

1 

18 

1 

20 

1 

Total  

162 

134 

126 

80 

68 

40 

43 

22 

15 

5 

7 

4 

1 

1 

708 

Average  number 
of  nigs  oer  litter 

7  ?, 

7  9 

8  4 

8  6 

9  3 

8  fi 

8  4 

8  ?, 

7  1 

10  6 

8  9 

7  8 

7  0 

7  0 

NOTE. — The  708  litters  contained  5,774  pigs,  an  average  of  8.1  pigs  per  litter. 
The  average  number  of  pigs  from  sows  1  and  1%  years  old  was  7.5  pigs. 
The  average  number  of  pigs  from  sows  2  years  old  or  over  was  8.6  pigs. 


BULLETIN  No.  226 


[May, 


TABLE  11. — RELATION  OP  WEIGHT  OP  PIGS  TO  SIZE  OP  LITTER  IN 
WHICH  FARROWED:  Females 


Weight 
per 

P.JS. 
26s. 

Number  of  pigs  per  litter 

Total 
number 
of 

litters 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

18 

20 

.7.  . 

1 
1 

2 

1 

4 
5 
3 
13 
10 
19 
26 
26 
46 
56 
.  53 
65 
80 
149 
100 
126 
158 
158 
209 
156 
163 
170 
93 
187 
80 
80 
60 
53 
55 
28 
20 
10 
4 
7 
2 
5 
1 
1 
1 
1 

2483 

8     .  .. 

1 

1 

1 

1 

?, 

.9  

..   1 

1  o  

1 

2 
1 
8 
8 
5 
3 
5 
8 
7 
23 
20 
23 
26 
22 
24 
17 
13 
24 
6 
21 
5 
7 
10 
7 
4 
3 
4 

5 

1 
2 
1 
7 
13 
7 
8 
14 
16 
25 
18 
15 
30 
26 
31 
35 
30 
22 
11 
33 
12 
10 
7 
7 
5 
2 
4 

2 
2 
1 
3 
2 
2 
5 
9 
9 
8 
19 
14 
20 
18 
18 
34 
22 
18 
16 
15 
15 
3 
1 
7 
3 
7 
2 

3 
2 
1 
3 
1 
7 
8 
8 
6 
10 
14 
14 
13 
13 
12 
19 
9 
12 
16 
7 
15 
10 
13 
5 
5 
1 
2 

1 
1 
1 
2 
1 
2 
9 
3 
6 
4 
10 
1 
4 
10 
5 
9 
5 
8 
6 
9 
7 
4 
5 
2 
2 
.... 

1 

1.1  

1 

1 

1.2  

1 
1 

1 
1 
1 

5 

"i 

2 
6 
1 
4 
3 
6 
3 
11 
9 
12 
16 
9 
14 
13 
7 
18 
7 
7 
5 
4 
5 
6 
1 
1 

2 
2 
2 
5 
6 
4 
7 
9 
17 
4 
11 
8 
17 
19 
16 
15 
20 
10 
16 
10 
9 
6 
2 
5 
1 
3 
3 
1 
1 
1 

"S 

'"e 

5 
6 
8 
11 
16 
15 
7 
21 
20 
29 
22 
25 
23 
11 
29 
13 
17 
9 
11 
10 
2 
4 

4 
2 
3 
2 
3 
3 
1 
3 
8 
4 
9 
5 
6 
11 
6 
7 
2 
1 
4 
2 
3 
1 

1.3  

14 

1.5  

1 

1 
1 

"3 
3 

"i 

i 

2 
1 
1 
1 
3 
1 
3 
2 

1.6  

1 

1 
4 
1 
2 
4 

1 

1.7  

1 

"i 

1 
1 

1.8  

19 

1 
1 

2 
1 

5 

2.0  

a 

"2 

i 

2.1  

2 
"l 

"i 

2.2  

1 

6 
8 
5 
4 
6 
3 
2 
5 
3 
1 
1 
2 
7 
6 
5 
1 
1 
1 

2 
7 
8 
5 
5 
10 
13 
9 
18 
6 
5 
2 
2 
5 
1  4 
3 
1 

2  3 

2.4  

2.5  

1 
1 

"2 

3 
3 

1 
1 
5 
1 
2 
1 
2 
2 
2 
1 

"i 
2 
1 

i 

"i 

i 

"i 

2 

2.6  

2.7  

i 

S 

2.8  

29. 

3.0  

l 
2 

"2 

i 

1 

3.1  

3.2  

3  3 

1 

1 
2 

i 

34 

3.5  

3 

i 

3.6  

3  7 

3  8 

1 

1 

2 

1 

39. 

1 
2 

4.0  

1 

V 

1 

4.1  

1 

4  2 

1 

1 

2 

1 

4  3 

1 

4  4 

1 

4.5  

1 

4.9    

1 

2 

125 

Total  

13 

30 

80 

177 

238 

327 

309 

400 

278 

234 

121 

M 

21 

11 

s 

12 

Percent  weighing  2 . 5  pounds  or  less '. 52 . 6 

Percent  weighing  over  2 . 5  pounds 47.4 

The  females  constituted  47 . 9  percent  of  the  total  number  of  pigs  farrowed. 


1980] 


VARIATIONS  IN  FARROW 


89 


TABLE  12. — RELATION  OF  WEIGHT  OP  PIGS  TO  SIZE  OP  LITTER  IN 
WHICH  FARROWED:    Males 


Weight 
per 

r»8- 
/6s. 

Number  of  pigs  per  litter 

Total 
number 
of 
litters 

1 

2 

8 

4 

£ 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

18 

20 

.2  

1 

1 
1 
2 
4  • 
2 
19 
13 
16 
14 
29 
42 
36 
48 
77 
73 
132 
104 
136 
150 
158 
213 
171 
171 
172 
132 
231 
108 
97 
80 
71 
67 
36 
28 
26 
12 
16 
6 
4 
4 
2 
1 

.4  

1 

.7.  .  , 

9, 

8  

1 

1 
1 

1 
1 

1 

.9  

1  0  

1 

3 
2 
3 

1 
3 
8 
3 
4 
10 
7 
16 
13 
16 
16 
21 
22 
15 
24 
24 
11 
35 
18 
12 
10 
15 
8 
6 
4 
3 

'  "2 
1 
1 

4 
1 
3 
3 
5 
6 
6 
7 
11 
8 
21 
11 
14 
15 
25 
22 
21 
16 
14 
15 
25 
10 
8 
11 
6 
6 
3 
1 
3 

ri 

1 

2 

4 

'"2 
5 

7 
6 
6 
10 
14 
16 
14 
22 
18 
16 
32 
23 
36 
34 
18 
33 
14 
7 
14 
9 
14 
6 
6 
8 
4 
3 
1 

5 
1 
1 
1 
2 
6 
6 
9 
9 
12 
13 
10 
21 
21 
21 
25 
16 
22 
25 
11 
26 
19 
10 
5 
4 
4 
1 
2 

:Vi 

''"•  1 

1 
2 
2 
2 
5 
2 
4 
7 
10 
6 
20 
13 
15 
14 
10 
18 
14 
3 
8 
12 
17 
7 
6 
5 
7 
6 
5 
2 
2 
1 

1 

'"2 
2 
4 
4 
2 
2 
10 
5 
6 
3 
8 
7 
11 
9 
12 
7 
10 
11 
8 
7 
9 
7 
2 
J 

1 
1 

"i 

1 
1 

1.1  

12 

1 
1 

1 

1 

1 
1 
3 

1 

1.3  

1 

1.4  

2 
3 

1.5  

1 

2 
2 
4 
4 
4 
3 
5 
6 
6 
8 
6 
7 
5 
5 
4 
10 
2 
7 
2 
3 
3 

i 

2 

1.6  

1 

1 
1 
1 

3 
5 
2 
3 
10 
9 
11 
9 
19 
13 
11 
4 
20 
11 
23 
8 
7 
4 
3 
5 
2 
4 

"i 

i 

2 
2 
5 

7 
16 
12 
10 
22 
16 
40 
30 
22 
18 
19 
21 
9 
17 
7 
7 
8 
9 
4 
2 
2 
5 
1 
1 

1.7.  . 

"i 
i 

4 
2 
2 
4 
1 
2 
1 

s 
"2 

4 

1 

1 
1 

1 

1.8  

1 

2 
4 

1.9  

1 

2.0  

? 

3 
3 
3 
8 
2 
3 
4 
7 
1 
2 
4 
5 
2 
6 
8 
4 

8 

2 
8 
5 
8 
4 
10 
11 
14 
10 
9 
16 
6 
10 
(3 
8 
0 

2.1  

"i 

i 

1 

"i 

"i 

1 

2.2  

1 
3 
1 
3 
8 
1 

2.3  

1 
3 
2 
2 

2.4  

2.5  

1 

2 
1 
5 
2 
1 
2 
1 

2 

1 

2.6  

2.7.  . 

1 

"i 

2 
1 

'  'i 

2.8  

2.9  

1 
2 

4 
8 
1 
1 

1 

3.O  
3.1.  . 

1 

3.2.  . 

1 

1 

3.3  

1 

3.4  

3 

i 

3.5.  . 

2 
1 

3.6 

3.7  

2 
2 
1 
2 
1 

1 
1 

"i 
1 
1 

o 

3  8 

1 

3 

1 

3.9.  . 

1 

4.0 

4.1  

---JT1 

4.2  

1 

1 

4.3  

1 

i 
1 

1 

4.4  .  .. 

1 

4.5  

1 

Total.  .  .  . 

3 

15 

27 

78 

144 

194 

320 

337 

306 

410 

310 

226 

156 

105 

35 

21 

10 

8 

2705 

Percent  weighing  2.5  pounds  or  less 46.8 

Percent  weighing  over  2 . 5  pounds 53 . 2 

The  males  constituted  52. 1  percent  of  the  total  number  of  pigs  farrowed. 


90 


BULLETIN  No.  226 


[May, 


TABLE  13. — RELATION  OF  WEIGHT  OF  PIGS  TO  SIZE;  OF  LITTER  IN 
WHICH  FARROWED:     Females  and  Males 


Number 
of  pigs 
per 
litter 

Females 

Males 

Total  number  studied 

Number 

Total 
weight, 

/6s. 

Average 
weight 
per 
pig. 
Ibs. 

Number 

Total 
weight, 

Ibs. 

Average 
weight 
per 
pig, 
Ibs. 

Number 

Total 
weight, 

Ibs. 

Average 
weight 
per 
Pig. 
Ibs. 

1.  . 

2 
13 
30 
80 
125 
177 
238 
327 
309 
400 
278 
234 
121 
94 
24 
11 
8 
12 

4.9 
39.0 
84.8 
216.6 
346.5 
463.5 
615.1 
853.7 
748.4 
974.9 
676.3 
569.6 
283.1 
215.2 
58.4 
26.1 
20.2 
29.0 

2.45 
3.00 
2.83 
2.71 
2.77 
2.62 
2.58 
2.61 
2.42' 
2.44 
2.43 
2.43 
2.34 
2.29 
2.43 
2.37 
2.53 
2.42 

3 
15 
27 

78 
144 
194 
320 
337 
306 
410 
310 
226 
156 
105 
35 
21 
10 
8 

7.4 
39.1 
76.0 
217.8 
406.7 
507.3 
862.2 
884.1 
763.4 
1070.4 
773.5 
559.2 
384.6 
264.3 
89.8 
50.7 
22.6 
21.5 

2.47 
2.61 
2.81 
2.79 
2.82 
2.61 
2.69 
2.62 
2.49 
2.61 
2.50 
2.47 
2.47 
2.52 
2.57 
2.41 
2.26 
2.69 

5 
28 
57 
158 
269 
371 
558 
664 
615 
810 
588 
460 
277 
199 
59 
32 
18 
20 

12.3 
78.1 
160.8 
434.4 
753.2 
970.8 
1477.3 
1737.8 
1511.8 
2045.3 
1449.8 
1128.8 
667.  7 
479.5 
148.2 
76.8 
42.8 
50.5 

2.46 
2.79 
2.82 
2.75 
2.80 
2.62 
2.65 
2.62 
2.46 
2.53 
2.47 
2.45 
2.41 
2.41 
2.51 
2.40 
2.38 
2.51 

2   

3  

4  

5  

6  

7  

8  

9  

10 

11  

12  

13  

14. 

15  

16  

18  

20  

Total  or 
average.  .  .  . 
Number  in 
litters  of  8 
pigs  or  less. 
Number  in 
litters  of 
more    than 
8  pigs  

2483 
992 

1491 

6225.3 
2624.1 

3601.2 

2.51 
2.65 

2.42 

2705 
1118 

1587 

7000.6 
3000.6 

4000.0 

2.59 
2.68 

2.52 

5188 
2110 

3078 

13225.9 
5624.7 

7601.2 

2.55 

2.67 

2.47 

TABLE  14. — RELATION  OF  AGE  OF  DAM  TO  BIRTH  WEIGHT  OF  PIGS 


Age  of  dam, 
years 

Number 
of  pigs 

Total  weight 
of  pigs, 
Ibs. 

Average  weight 
per  pig, 
/6s. 

1.  . 

992 
977 
951 
647 
594 
328 
315 
171 
99 
53 
53 
18 
7 
7 

2415.7 
2396.9 
2429.0 
1672.0 
1541.2 
868.3 
813.6 
462.4 
281.2 
150.5 
143.4 
54.0 
15.9 
25.0 

2.44 
2.45 
2.55 
2.58 
2.59 
2.65 
2.58 
2.70 
2.84 
2.84 
2.71 
3.00 
2.27 
3.57 

1J£.  . 

2    ... 

2M  

3.  . 

3^.  .. 

4 

4M.  . 

5    ... 

5%  

6.  . 

6>$.. 

7   ... 

8  

Total  

5212 

13269  .  1 

2.55 

Average  weight  of  pigs  from  BO\ 
Average  weight  of  pies  from  so 

vs  1  and  1J^  years  old  

2.44 
2.61 

ivs  2  years  old  or  over.  .  . 

1920] 


VARIATIONS  IN  FARROW 


91 


TABLE  15. — RELATION  OF  AGE  OP  DAM  TO  NUMBER  OF  PIGS  FARROWED 
DEAD  OR  IMMATURE 


Age  of  dam, 
years 

Number  of  pigs  farrowed  by  sows  of  these  ages 

Dead 

Immature 

Total  number 
dead  or 
immature 

Total  number 
studied 

Percent  dead 
or  immature 

1. 

69 
66 
51 
38 
66 
26 
19 
19 
22 
10 
2 
5 

38 
17 
31 
12 
21 
13 
9 
6 

'i 

3 

107 
83 
82 
50 
87 
3» 
28 
25 
22 
10 
3 
8 

1174 
1058 
1056 
690 
635 
342 
375 
181 
107 
53 
62 
31 
7 
7 

9.1 
7.8 
7.8 
7.2 
13.7 
11.4 
7.5 
13.8 
20.6 
18.9 
4.8 
25.8 

\yz  

2  

2K 

3      .. 

3J^  

4.  . 

4K 

5  .  : 

5>^  

6  

6>6  

7  

8  

Total 

393 

151 

544 

5778 

9.4 

Percentage  of  pigs  farrowed  dead  or  immature  from  sows  1  to  2J^  ye 
Percentage  of  pies  farrowed  dead  or  immature  from  sows  3  years  ok 

ars  old  

8.1 
12.3 

or  over  .  .  . 

TABLE  16. — RELATION  OF  AGE  OF  DAM  TO  SEX  OF  PIGS 


Age  of  dam, 
years 

Number  of  pigs  of 
each  sex 

Number  of  pigs, 
sex  of  which 
was  not  obtained 

Total  number 
studied 

Females 

Males 

1..  . 

547 
497 
487 
331 
298 
162 
143 
88 
48 
19 
37 
11 
1 
4 

580 
544 
530 
347 
327 
167 
195 
89 
59 
34 
24 
17 
6 
3 

47 
17 
39 
12 
10 
13 
25 
4 

'i 

3 

1174 
1058 
1056 
690 
635 
342 
375 
181 
107 
53 
62 
31 
7 
7 

\yz  

2  

2>^  

3  

3H  

4  

4^  .... 

5  

5^  

6  

6J^  

8  

Total  

2673 

2922 

171 

5778 

Percent  .  . 

47.8 

52.2 

Percent  from  sows  1  and  1J^  years  ol 
Percent  from  sows  2  years  old  and  ov 

TABLE  17.—  TOTAL 

d  

Females                        Males 
48.2                            51.8 
47.5                            52.5 

OF  EACH  BREED 

er  

NUMBER  OF  LITTERS 

Berkshire  

363 
37 

78 
4 
67 

Tamworth 
Large  Yorl 
Crossbred  ' 
Unknown2 

40 
35 

77 
20 

Chester  White  

cshire  

Duroc-Jersey  

Total  .  . 

720 

bred. 


All  litters  in  which  the  pigs  were  cross-bred,  regardless  of  breeding  of  dams,  are  listed  as  cross- 


2 All  litters,  in  which  the  breeding  is  not  definitely  known,  are  listed  as  unknown. 


92 


BULLETIN  No.  226 


[May, 


a 
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Number 
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Breeding 

Berkshire  
Chester  White  
Duroo-Jersey  
Hampshire  
Poland  China  
Tamworth  
Large  Yorkshire  
Crossbred  

Average  or  total  

1 

Average 
per  pig, 
Ibs. 

SSSSSSSfcSS 

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Average 
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1980] 


VARIATIONS  IN  FARROW 


93 


TABLE  20. — RELATION  OF  ORDER  OP  FARROWING  TO  SEX  AND  WEIGHTS  OF  PIGS 

(261  LITTERS) 


Weight. 
Ibs. 


FIRST  FARROWED 


Females 


Males 


Total 


LAST  FARROWED 


Females 


Males 


Total 


.8 

.9 

1.0 1 

1.1 1 

1.2 

.3 3 

.4 

.5 2 

.6 3 

.7 1 

.8 2 

.9 4 

2.0 9 

2.1 7 

2.2 8 

2.3 3 

2.4 8 

2.5 5 

2.6 6 

2.7 8 

2.8 6 

2.9 3 

3.0 6 

3.1 4 

3.2 1 

3.3 2 

3.4 2 

3.5 5 

3.6 3 

3.7 

3.8 

3.9 1 

4.0 2 

4.4 

Total 106 

Average  weight 2.50 

Percent 40.6 


1 

1 

'i 

2 

2 

1 

3 

2 

8 

4 

7 

6 

9 

12 

11 

12 

14 

6 

15 

7 

9 

5 

7 

5 

1 

1 


1 

2 

1 

3 

1 

4 

5 

2 

5 

6 

17 

11 

15 

9 

17 

17 

17 

20 

20 

9 

21 

11 

10 

7 

9 

10 

4 

1 

'i 

3 

1 


1 

2 

1 
2 
3 
2 

'5 

4 
4 
8 

11 
3 
6 
5 
6 

10 
7 

10 
7 
4 
8 
7 
5 
1 
2 


2 

6 
3 

'3 
5 
6 
7 
6 
4 

11 

18 
8 
4 
9 
6 

11 
3 
2 
4 
3 
2 
2 
1 

'i 

1 


1 

1 

4 

1 

4 

3 

4 

6 

8 

4 

7 

13 

17 

10 

12 

9 

17 

28 

15 

14 

16 

10 

19 

10 

7 

5 

5 

2 

4 

1 

1 

1 

2 


155 


261 


128 


133 


261 


2.67 
59.4 


2.60 


2.39 
49.0 


2.48 
51.0 


2.43 


Number  of  pigs  weighing 
2.5  pounds  or  less 

Number  of  pigs  weighing 
over  2 . 5  pounds 


57 
49 


60 
95 


117 
144 


73 

55 


76 
57 


149 
112 


NOTE. — The  grand  average  weight  of  all  the  pigs  in  the  261  litters  was  2.54  pounds. 


94 


BULLETIN  No.  226 


[May, 


TABLE  21. — DATA  CONCERNING  SUCCEEDING  LITTERS  FROM  THE  SAME  Sows 


Litter  

1 

2 

3 

4 

5 

6 

7 

8 

9 

Aver- 
age 

AVERAGE  OF  246  Sows  WITH  ONE  LITTER  EACH 

1.2 

1.2 
114.5 
7.2 
17.4 
2.41 

Length  of  gestation  period.  .  .  . 

114.5 

Number  of  pigs  per  litter  

7.2 

17  4 

Weight  per  pig  

2.41 

AVERAGE  or  152  Sows  WITH  Two  LITTERS  EACH 


1.2 

2  0 

1.6 

Length  of  gestation  period.  .  .  . 

114.8 

114.4 

114.6 

Number  of  pigs  per  litter  

7.4 

8.4 

7.9 

Weight  per  litter  

17.9 

21.5 

19.7 

Weight  per  pig  

2.38 

2.55 

2.47 

AVERAGE  OF  84  Sows  WITH  THREE  LITTERS  EACH 


Age  of  sows  

1.2 

2.0 

2.7 



1.9 

Length  of  gestation  period.  .  .  . 

115.1 

7.7 

114.3 
9.0 

114.5 

8.7 

114.6 
8.5 

Weight  per  litter  

18.3 

22.7 

22.7 

: 

21.3 

Weight  per  pig  

2.36 

2.54 

2.64 

2.52 

AVERAGE  OF  51  Sows  WITH  FOUR  LITTERS  EACH 


Age  of  sows  .  .•'  

1.2 

2.0 

2.7 

3.3 

2.3 

Length  of  gestation  period.  .  .  . 

114.9 
7.7 

114.7 
8.9 

114.4 
8.7 

114.8 
9.4 



114.6 
8.7 

Weight  per  litter  

18.5 

22.0 

22.0 

23.1 

21.4 

Weight  per  pig  

2.36 

2.50 

2.60 

2.59 

2.52 

AVERAGE  OF  35  Sows  WITH  FIVE  LITTERS  EACH 


Age  of  sows  

1.1 

2.0 

2.6 

3.2 

3.8 

2.5 

Length  of  gestation  period.  .  .  . 

114.7 
7.7 

114.5 
8.9 

114.3 
8.9 

114.7 
9.8 

115.0 
9.3 

114.6 
8.9 

Weight  per  litter  

18.9 

22.5 

23.1 

24.6 

23.6 

22.5 

Weight  per  pig  

2.38 

2.61 

2.66 

2.61 

2.67 

2.59 

AVERAGE  OF  22  Sows  WITH  Six  LITTERS  EACH 


Age  of  sows  

1.1 

1.9 

2.5 

3.2 

3.8 

4.4 

'' 

2.8 

114.4 

114.6 

114.5 

114.9 

115  0 

114  6 

114.6 

Number  of  pigs  per  litter  

8.0 

8.7 

9.1 

10.0 

9.5 

9.6 

9.2 

Weight  per  litter  

19.0 

23.0 

23.6 

25.9 

24.6 

24.7 

23.4 

Weight  per  pig  

2.40 

2.62 

2.68 

2.69 

2.71 

2.61 

2.62 

AVERAGE  OF  13  Sows  WITH  SEVEN  LITTERS  EACH 


1.1 

2  0 

2  6 

3  3 

3  9 

4  5 

5  2 

3  2 

Length  of  gestation  period.  .  .  . 

115.1 

114.5 

114.8 

114  8 

114  9 

115.3 

113  4 

114.7 

Number  of  pigs  per  litter  
Weight  per  litter  

7.8 
18.9 

9.1 
23.2 

8.8 
23.9 

9.6 
26.7 

9.1 
23.7 

9.1 
24.5 

7.7 
21.4 

8.7 
23.2 

Weight  per  pig  

2.43 

2.60 

2.76 

2.78 

2.88 

2.77 

2.67 

2.70 

AVERAGE  OF  5  Sows  WITH  EIGHT  LITTERS  EACH 


Age  of  sows  

1.1 

2.0 

2.6 

•    3.2 

3.7 

4.3 

4.7 

5.5 

3.4 

Length  of  gestation  period  
Number  of  pigs  per  litter  

115.3 
6.2 
16  7 

114.4 
9.2 
23  0 

114.6 
8.8 
22  7 

114.3 
8.6 
24  6 

114.3 
8.2 
22  7 

113.8 
9.4 
23  2 

114.8 
7.2 
19  8 

115.0 
8.4 
23  2 

114.5 
8.3 
21  9 

Weight  per  pig  

2.70 

2.55 

2.75 

2.87 

2.83 

2.63 

2.74 

2.83 

2.73 

AVERAGE  OF  3  Sows  WITH  NINE  LITTERS  EACH 


1  2 

2  0 

2  5 

3  0 

3  5 

4  2 

4  7 

5  5 

6  3 

3  6 

Length  of  gestation  period.  .  .  . 
Number  of  pigs  per  litter  
Weight  per  litter  

116.0 
4.7 
12.2 

115.0 
8.0 
20.1 

115.3 
8.0 
23.0 

114.0 

7.7 
22.0 

113.5 
7.3 
20.9 

114.0 

7.7 
19.0 

116.0 
7.3 
21.5 

117.5 
7.7 
21.0 

116.0 
9.7 
25.6 

115.3 
7.6 
20.5 

Weight  per  pig  

2.61 

2.63 

2.87 

2.87 

2.85 

2.85 

2.94 

2.87 

2.95 

2.84 

Age  is  given  in  years;  gestation  period  in  days;  weight  in  pounds. 


VARIATIONS  IN  FARROW 


95 


TABLE  22. — DATA  CONCERNING  SUCCEEDING  LITTERS  PROM  THE  SAME  Sows  AT 

DIFFERENT  AGES 


Sows  WITH  ONE  LITTER  EACH 

Sows  farrowing  first  litter  at  

1  yr. 

153 

74 

Length  of  gestation  period  

114.7 

114.1 

Number  of  pigs  per  litter  

7  15 

7  35 

Weight  per  litter  

16  9 

17  9 

Weight  per  pig  

2.40 

2.44 

Sows  WITH  Two  LITTERS  EACH 


43  Sows:    Age  at  farrowing  

1  yr. 

11A  yrs. 

Ai>er. 

Length  of  gestation  period  .    . 

114  9 

114  4 

114  7 

Number  of  pigs  per  litter  

7  21 

8  72 

7  96 

Weight  per  litter  

16  1 

22  3 

19.3 

Weight  per  pig  

2.26 

2.51 

2.41 

53  Sows:  Age  at  farrowing  

1  yr. 

2  yrs. 

Length  of  gestation  period  

114.7 

114  0 

114.4 

Number  of  pigs  per  litter,  

7  70 

8  11 

7  91 

Weight  per  litter  

18  8 

22  2 

20.4 

Weight  per  pig  

2  40 

2.54 

2.47 

28  Sows:     Age  at  farrowing  

2  yrs 

Aver. 

Length  of  gestation  period  ;  

114  8 

114  7 

114.8 

6  71 

7  93 

7  32 

Weight  per  litter  . 

16  3 

21  2 

18  6 

Weight  per  pig  

2.46 

2.61 

2.54 

Sows  WITH  THREE  LITTERS  EACH 


14  Sows:     Age  at  farrowing  

1  yr. 

/}/£  yrs. 

%  yrs. 

Length  of  gestation  period  

114.3 

114   1 

114  8 

114  4 

Number  of  pigs  per  litter  

7.64 

8.57 

9.64 

8  62 

Weight  per  litter  

16.7 

22.3 

23  0 

20  5 

Weight  per  pig  

2  19 

2  63 

2  48 

2  44 

9  Sows:     Age  at  farrowing  

11A  yr. 

#  yrs. 

2%  yrs. 

Length  of  gestation  period  

114.6 

114.7 

114.0 

114  4 

Number  of  pigs  per  litter  

6  89 

8  56 

8  89 

8  11 

Weight  per  litter  

16  4 

21  8 

23  6 

20  4 

Weight  per  pig  

2.38 

2.67 

2.66 

2  57 

22  Sows:     Age  at  farrowing  

1  yr. 

%  yrs. 

#l/ij  yrs. 

Length  of  gestation  period  

114.9 

114.0 

114.7 

114  5 

Number  of  pigs  per  litter  

8.05 

10.27 

9.05 

9  12 

Weight  per  litter  

19  1 

24  3 

24  3 

22  5 

Weight  per  pig  

2.37 

2  50 

2  64 

2  51 

11  Sows:     Age  at  farrowing  

2  yrs. 

3  yrs. 

Length  of  gestation  period  

112.7 

113  6 

114  5 

113  8 

Number  of  pigs  per  litter  

8.27 

9.64 

8.82 

8  91 

Weight  per  litter  ... 

20  3 

24  7 

23  7 

23  0 

Weight  per  pig  

2.42 

2.56 

2.70  - 

2.56 

Sows  WITH  FOUR  LITTERS  EACH 


7  Sows  :    Age  at  farrowing  

1  yr. 

1%  yrs. 

2  yrs. 

2%  yrs. 

Length  of  gestation  period  

113.5 

114.0 

114.8 

114.8 

114  3 

Number  of  pigs  per  litter  

7  86 

10  29 

10  57 

10  43 

9  79 

Weight  per  litter  

19.1 

25.4 

24.5 

24  2 

23  3 

Weight  per  pig  

2.43 

2.54 

2.45 

2.32 

2  42 

5  Sows  :     Age  at  farrowing  

1%  yrs'. 

2  yrs. 

#Jlj  yrs. 

3  yrs. 

Length  of  gestation  period    .    ... 

115  3 

114  6 

113  4 

114  0 

114  3 

Number  of  pigs  per  litter  

8  60 

10.40 

9  00 

9  00 

9  25 

Weight  per  litter  

19.8 

25.6 

24.8 

22.4 

22  9 

Weight  per  pig  

2.30 

2.56 

2.76 

2.49 

2.52 

13  Sows:     Age  at  farrowing  

1  yr. 

#  yrs. 

#K  vrs. 

3  yrs. 

Aver. 

Length  of  gestation  period  

114  6 

113  8 

114  5 

114  4 

114  3 

Number  of  pigs  per  litter  

7.46 

10.00 

9.31 

10.62 

9  35 

Weight  per  litter  

17.0 

20.7 

23.7 

25.8 

21.7 

Weight  per  pig  

2.31 

2.36 

2.46 

2.67 

2.51 

Length  of  gestation  period  is  given  in  days;  weight  in  pound 


UNIVERSITY  OF  ILLINOIS-URBANA 


